1. Field of the Invention
The present invention relates to an ultrasonic probe including a transmitting circuit mounted therein and an ultrasonic diagnostic apparatus.
2. Description of the Related Art
An ultrasonic probe including a 1.5 dimensional array or a two dimensional array having elements larger than the number of channels (for example, 128 channels) of an ultrasonic diagnostic apparatus main body has been developed.
In JP-A-2000-33087, an example that processes signals by dividing an ultrasonic oscillator into groups of a plurality of sub arrays.
In the above ultrasonic probe, it has been studied for disposing a transmitting circuit or a receiving circuit corresponding to the respective oscillators in a probe handle, bundling receiving signals by dividing the vibrates into groups of a plurality of sub arrays in the probe handle and not increasing the number of connecting signals to the ultrasonic diagnostic apparatus main body.
For example, in a two dimensional array probe including 3200 elements, when a group consists of 25 receiving elements, it is possible to control 3200 elements by 128 groups, and further possible to connect the main body having 128 channels. Further, in the groups, the electronic scan can be performed by minutely controlling a delay time corresponding to a direction of a receiving beam.
The delay time is controlled by a transmitting beam former provided in the probe handle and a high voltage pulse is generated from a transmitting circuit provided in every element. By using a serial bus between the device main body and the transmitting beam former, it is possible to transfer delay data and waveform data via a plurality of control lines.
However, in the ultrasonic probe that includes a transmitting and receiving circuit in the probe handle, heat generated due to a conversion loss of the ultrasonic oscillator and the heat generated due to the power consumption of the electronic circuit can not be avoided. Therefore, it is required to reduce the amount of the generated heat. Further, it is required to reduce the size and the weight of the probe handle so as to prevent the fatigue caused when grasping for a long time. Therefore, a small and low power consumption circuit is used as an electronic circuit in the probe, and the transmitting circuit is configured by a simple monopolar pulse driving circuit.
The clinical demand on harmonic imaging having a high resolution increases, and a method such as a pulse inversion imaging method is preferably used. The pulse inversion imaging method transmits twice a signal whose phase is shifted by 180 degrees and adds two echo signals on the basis of the twice transmission to extract only a harmonic component and then create an image.
However, since the general monopolar pulse driving circuit can not output a bipolar waveform, the pulse inversion imaging method can not used. Therefore, when the transmitting circuit is configured by the monopolar pulse driving circuit, a harmonic imaging method that uses a filtering method for removing a fundamental wave by the high pass filter is used. In the filtering method, the transmitting fundamental wave is uncontrollably removed, and the image quality is worse than that of the pulse inversion imaging method.
In JP-A-2004-89694, it is disclosed that an electrode opposite to an electrode of an ultrasonic oscillator to which a transmitting circuit is connected to a receiving circuit so that the pulse inversion imaging method can be used in the monopolar pulse driving circuit.
However, according to the configuration disclosed in JP-A-2004-89694, due to the difference in the characteristics of the P channel transistor, the N channel transistor and probe cable, the rising time and the falling time are different from each other. Therefore, the symmetrical property of the sinusoidal wave becomes deteriorated.
According to the related art, when the monopolar pulse driving is used, the bipolar waveform can not be output. Even when the bipolar waveform is output, the symmetrical property of the waveform is bad, and it is difficult to obtain a higher quality image than that of the pulse inversion imaging method.